Joseph Parker has achieved his childhood dream of becoming the heavyweight champion of the world.

In an extraordinarily close fight in which Parker fought mostly on the back foot for all 12 rounds, prevailed by decision over Mexican Andy Ruiz Jr.

It was a clash of styles - Ruiz Jr wanted a brawl, Parker clearly wanted to outbox. In the end he won by the closest of margins - majority decision.

His corner, in the ring for the decision, erupted at the result. Judges Salven Lagumbay scored it 114-114, and Ramon Cerdan and Ingo Barrabas scored it 115-113.

Ruiz Jr was extremely gracious in the ring afterwards and will New Zealand with the respect of the country. He is one tough customer.

"New Zealand, thank you," Parker said in the ring.

"A dream come true," he said. "Thanks you to Andy Ruiz and his team for putting on a hard fight. I told you Andy was a great fighter with a lot of speed and he showed that tonight."

Trainer Kevin Barry said: "I told him to stick to the game plan, not follow Andy's." Parker did.

He showed enormous confidence and belief in himself and his game plan by not being too impatient, despite his slow start.

Ruiz Jr won perhaps the first three or four rounds before Parker came back into it, scoring with his razor-sharp jab and occasionally with his right hand.

Parker's first outright winning round was the fifth, and the crowd's cheering of every punch he landed would have helped.

In the sixth he found his range nicely, keeping Ruiz Jr at distance, but both men traded with about 30 seconds left.

Parker, keeping Ruiz Jr away with relative ease now, created a graze above Ruiz Jr's right eye in the seventh but couldn't capitalize and it was another extremely close round.

Round eight and nine was again very close, with Parker perhaps shading the latter. Parker won the 10th, landing several big right hands, but Ruiz Jr showed an extraordinary toughness in comfortably shaking them off. Parker shaded the 11th, landing a beautiful left, right combination.

Both men were unhurt and clearly expecting the fight to go the distance. The final, championship, round belonged to Parker, but it would have been an extremely nervous waight for him and his team until referee Tony Weeks raised his hand as the new WBO heavyweight champion.

"Joseph is going to have a break because he really deserves some time off," Barry said.

This was his man's fifth fight of the year and he looked a little flat at times.

The break looks deserved. Turning professional only four years ago, Parker has created history.

He is the first New Zealand-born fighter to win a world heavyweight title. His victory also makes the 24-year-old south Aucklander one of the youngest to win the title for the first time.

Mike Tyson holds the record with his victory over Trevor Berbick as a 20-year-old, but Parker easily makes the top 10 alongside the likes of Michael Moorer and Leon Spinks, both of whom reached the summit at 24.

Parker is now undefeated after 22 professional fights and has the world as his feet. Ruiz Jr, who trained as hard as he ever has for this fight, moves to a 29-1 record.

In front of a crowd of 10,000 and a worldwide audience of millions, Parker walked to the ring with a smile on his face and delivered what he promised to do; a triumph which will resonate here and around the globe.

As usual he was incredibly relaxed before the fight. Before he watched his younger brother, John, win his catchweight contest against Ash McConville in the first televised bout of the evening, he sent a text to his promoter and friend David Higgins.

The gist of it was that he had a "special feeling", and that victory was "meant to be".

This victory was also a victory for trainer Kevin Barry, the man who took David Tua to a heavyweight world title challenge against Lennox Lewis in Las Vegas in 2000, only to see his fighter miss out.

Parker will now have top heavyweights Anthony Joshua and Deontay Wilder, who hold two other versions of the title, in his sights, plus Wladimir Klitschko, the former IBF, WBO and WBA champion.